Ben B. wrote: ↑Tue Apr 14, 2020 1:46 am
I’ve spoken with 2 ballisticians at powder companies. Both indicated that “reading pressure signs” is essentially witchcraft, akin to reading chicken entrails to forecast the future. Sometimes “pressure signs” show up at low measured pressure and sometimes they never show when measured pressure is well over max. Too many variables at play to count on pressure signs. But I still check...
Not sure it’s as bad as reading chicken guts, but it’s a point well taken.
It seems in general that by the time you get undeniable pressure signs, you were getting high pressure about two loads in the ladder ago. Measuring case web expansion is probably the best way.
Using a low pressure/thin cup primer in a high pressure load explains some of the cratering, but when your load is about 8% less than max, and your velocity is 8% over predicted max with pressure signs starting to appear, it’s time to be careful.
I think that’s more the point I’m trying to make. I don’t see a reason to stop there based on brass and primers. I do see good reason to take more care.
Another variable that can create over pressure signs is the weight of the brass used, a direct correlation to powder capacity. For example there are some head stamps where each case can weigh 100-104+ grains(.223/5.56). The IMI '13' 5.56 cases I loaded this morning with CFE and 40 gr Vmax averaged very close to 96 gr. This is not a powder that produces the pressure per grain of most ball powders. A heavier case and a hot load of say H335 and bullets seated 0.020 deeper than the max listed OAL...would very likely have high pressure warning signs or blown primer in a .223 chamber.
One young hand loader came to me with his 300 BLK brass made from one of the heaviest and thick neck on the list. He was having all manner of issues and after managing to get some to chamber he was puzzled by the poor feeding and primers very flat. His load of H110 would have been fine reduced by 2 grains, but the thick and heavy case body was a non starter. In all my .223 loads the brass is checked for a weight range, the BLK brass is only made from LC and a few commercial ones known to be pretty consistent.
Dellet has certainly covered seating depth and case fill and the brass capacity as well.
